Sounding reference signal subframe position in a plurality of scheduled consecutive subframes

ABSTRACT

A wireless device receives a radio resource control message comprising an aperiodic sounding reference signal (SRS) subframe parameter. A downlink control information is received. The downlink control information indicates uplink resources in a plurality of scheduled consecutive subframes for transmission of transport blocks by the wireless device and triggers an SRS transmission in a subframe of the plurality of scheduled consecutive subframes. The SRS is transmitted in the subframe. A position of the subframe in the plurality of scheduled consecutive subframes is determined based on the aperiodic SRS subframe parameter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/247,902, filed Jan. 15, 2019 (now U.S. Pat. No. 10,659,208, issuedMay 19, 2020), which is a continuation of U.S. patent application Ser.No. 15/422,452, filed Feb. 1, 2017, (now U.S. Pat. No. 10,187,187,issued Jan. 22, 2019), which claims the benefit of U.S. ProvisionalApplication No. 62/289,800, filed Feb. 1, 2016, and U.S. ProvisionalApplication 62/314,676, filed Mar. 29, 2016, all of which are herebyincorporated by reference in their entireties.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Examples of several of the various embodiments of the present disclosureare described herein with reference to the drawings.

FIG. 1 is a diagram depicting example sets of OFDM subcarriers as per anaspect of an embodiment of the present disclosure.

FIG. 2 is a diagram depicting an example transmission time and receptiontime for two carriers in a carrier group as per an aspect of anembodiment of the present disclosure.

FIG. 3 is an example diagram depicting OFDM radio resources as per anaspect of an embodiment of the present disclosure.

FIG. 4 is an example block diagram of a base station and a wirelessdevice as per an aspect of an embodiment of the present disclosure.

FIG. 5A, FIG. 5B, FIG. 5C and FIG. 5D are example diagrams for uplinkand downlink signal transmission as per an aspect of an embodiment ofthe present disclosure.

FIG. 6 is an example diagram for a protocol structure with CA and DC asper an aspect of an embodiment of the present disclosure.

FIG. 7 is an example diagram for a protocol structure with CA and DC asper an aspect of an embodiment of the present disclosure.

FIG. 8 shows example TAG configurations as per an aspect of anembodiment of the present disclosure.

FIG. 9 is an example message flow in a random access process in asecondary TAG as per an aspect of an embodiment of the presentdisclosure.

FIG. 10 is an example diagram depicting a downlink burst as per anaspect of an embodiment of the present disclosure.

FIG. 11 is an example diagram depicting an example multi-subframe grant,LBT process, and multi-subframe transmission as per an aspect of anembodiment of the present disclosure.

FIG. 12 is an example diagram depicting an example multi-subframe grant,LBT process, and multi-subframe transmission as per an aspect of anembodiment of the present disclosure.

FIG. 13 is an example diagram depicting an example multi-subframe grant,LBT process, and multi-subframe transmission as per an aspect of anembodiment of the present disclosure.

FIG. 14 is an example flow diagram illustrating as per an aspect of anembodiment of the present disclosure.

FIG. 15 is an example flow diagram illustrating an aspect of anembodiment of the present disclosure.

FIG. 16 is an example flow diagram illustrating an aspect of anembodiment of the present disclosure.

FIG. 17 is an example flow diagram illustrating an aspect of anembodiment of the present disclosure.

FIG. 18 is an example flow diagram illustrating an aspect of anembodiment of the present disclosure.

FIG. 19 is an example flow diagram illustrating an aspect of anembodiment of the present disclosure.

FIG. 20 is an example flow diagram illustrating an aspect of anembodiment of the present disclosure.

FIG. 21 is an example flow diagram illustrating an aspect of anembodiment of the present disclosure.

FIG. 22 is an example flow diagram illustrating an aspect of anembodiment of the present disclosure.

FIG. 23 is an example flow diagram illustrating an aspect of anembodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

Example embodiments of the present disclosure enable operation ofcarrier aggregation. Embodiments of the technology disclosed herein maybe employed in the technical field of multicarrier communicationsystems.

The following Acronyms are used throughout the present disclosure:

ASIC application-specific integrated circuit

BPSK binary phase shift keying

CA carrier aggregation

CSI channel state information

CDMA code division multiple access

CSS common search space

CPLD complex programmable logic devices

CC component carrier

DL downlink

DCI downlink control information

DC dual connectivity

EPC evolved packet core

E-UTRAN evolved-universal terrestrial radio access network

FPGA field programmable gate arrays

FDD frequency division multiplexing

HDL hardware description languages

HARQ hybrid automatic repeat request

IE information element

LAA licensed assisted access

LTE long term evolution

MCG master cell group

MeNB master evolved node B

MIB master information block

MAC media access control

MAC media access control

MME mobility management entity

NAS non-access stratum

OFDM orthogonal frequency division multiplexing

PDCP packet data convergence protocol

PDU packet data unit

PHY physical

PDCCH physical downlink control channel

PHICH physical HARQ indicator channel

PUCCH physical uplink control channel

PUSCH physical uplink shared channel

PCell primary cell

PCell primary cell

PCC primary component carrier

PSCell primary secondary cell

pTAG primary timing advance group

QAM quadrature amplitude modulation

QPSK quadrature phase shift keying

RBG Resource Block Groups

RLC radio link control

RRC radio resource control

RA random access

RB resource blocks

SCC secondary component carrier

SCell secondary cell

Scell secondary cells

SCG secondary cell group

SeNB secondary evolved node B

sTAGs secondary timing advance group

SDU service data unit

S-GW serving gateway

SRB signaling radio bearer

SC-OFDM single carrier-OFDM

SFN system frame number

SIB system information block

TAI tracking area identifier

TAT time alignment timer

TDD time division duplexing

TDMA time division multiple access

TA timing advance

TAG timing advance group

TB transport block

UL uplink

UE user equipment

VHDL VHSIC hardware description language

Example embodiments of the disclosure may be implemented using variousphysical layer modulation and transmission mechanisms. Exampletransmission mechanisms may include, but are not limited to: CDMA, OFDM,TDMA, Wavelet technologies, and/or the like. Hybrid transmissionmechanisms such as TDMA/CDMA, and OFDM/CDMA may also be employed.Various modulation schemes may be applied for signal transmission in thephysical layer. Examples of modulation schemes include, but are notlimited to: phase, amplitude, code, a combination of these, and/or thelike. An example radio transmission method may implement QAM using BPSK,QPSK, 16-QAM, 64-QAM, 256-QAM, and/or the like. Physical radiotransmission may be enhanced by dynamically or semi-dynamically changingthe modulation and coding scheme depending on transmission requirementsand radio conditions.

FIG. 1 is a diagram depicting example sets of OFDM subcarriers as per anaspect of an embodiment of the present disclosure. As illustrated inthis example, arrow(s) in the diagram may depict a subcarrier in amulticarrier OFDM system. The OFDM system may use technology such asOFDM technology, DFTS-OFDM, SC-OFDM technology, or the like. Forexample, arrow 101 shows a subcarrier transmitting information symbols.FIG. 1 is for illustration purposes, and a typical multicarrier OFDMsystem may include more subcarriers in a carrier. For example, thenumber of subcarriers in a carrier may be in the range of 10 to 10,000subcarriers. FIG. 1 shows two guard bands 106 and 107 in a transmissionband. As illustrated in FIG. 1, guard band 106 is between subcarriers103 and subcarriers 104. The example set of subcarriers A 102 includessubcarriers 103 and subcarriers 104. FIG. 1 also illustrates an exampleset of subcarriers B 105. As illustrated, there is no guard band betweenany two subcarriers in the example set of subcarriers B 105. Carriers ina multicarrier OFDM communication system may be contiguous carriers,non-contiguous carriers, or a combination of both contiguous andnon-contiguous carriers.

FIG. 2 is a diagram depicting an example transmission time and receptiontime for two carriers as per an aspect of an embodiment of the presentdisclosure. A multicarrier OFDM communication system may include one ormore carriers, for example, ranging from 1 to 10 carriers. Carrier A 204and carrier B 205 may have the same or different timing structures.Although FIG. 2 shows two synchronized carriers, carrier A 204 andcarrier B 205 may or may not be synchronized with each other. Differentradio frame structures may be supported for FDD and TDD duplexmechanisms. FIG. 2 shows an example FDD frame timing. Downlink anduplink transmissions may be organized into radio frames 201. In thisexample, the radio frame duration is 10 msec. Other frame durations, forexample, in the range of 1 to 100 msec may also be supported. In thisexample, each 10 ms radio frame 201 may be divided into ten equallysized subframes 202. Other subframe durations such as 0.5 msec, 1 msec,2 msec, and 5 msec may also be supported. Subframe(s) may consist of twoor more slots (for example, slots 206 and 207). For the example of FDD,10 subframes may be available for downlink transmission and 10 subframesmay be available for uplink transmissions in each 10 ms interval. Uplinkand downlink transmissions may be separated in the frequency domain.Slot(s) may include a plurality of OFDM symbols 203. The number of OFDMsymbols 203 in a slot 206 may depend on the cyclic prefix length andsubcarrier spacing.

FIG. 3 is a diagram depicting OFDM radio resources as per an aspect ofan embodiment of the present disclosure. The resource grid structure intime 304 and frequency 305 is illustrated in FIG. 3. The quantity ofdownlink subcarriers or RBs (in this example 6 to 100 RBs) may depend,at least in part, on the downlink transmission bandwidth 306 configuredin the cell. The smallest radio resource unit may be called a resourceelement (e.g. 301). Resource elements may be grouped into resourceblocks (e.g. 302). Resource blocks may be grouped into larger radioresources called Resource Block Groups (RBG) (e.g. 303). The transmittedsignal in slot 206 may be described by one or several resource grids ofa plurality of subcarriers and a plurality of OFDM symbols. Resourceblocks may be used to describe the mapping of certain physical channelsto resource elements. Other pre-defined groupings of physical resourceelements may be implemented in the system depending on the radiotechnology. For example, 24 subcarriers may be grouped as a radio blockfor a duration of 5 msec. In an illustrative example, a resource blockmay correspond to one slot in the time domain and 180 kHz in thefrequency domain (for 15 KHz subcarrier bandwidth and 12 subcarriers).

FIG. 5A, FIG. 5B, FIG. 5C and FIG. 5D are example diagrams for uplinkand downlink signal transmission as per an aspect of an embodiment ofthe present disclosure. FIG. 5A shows an example uplink physicalchannel. The baseband signal representing the physical uplink sharedchannel may perform the following processes. These functions areillustrated as examples and it is anticipated that other mechanisms maybe implemented in various embodiments. The functions may comprisescrambling, modulation of scrambled bits to generate complex-valuedsymbols, mapping of the complex-valued modulation symbols onto one orseveral transmission layers, transform precoding to generatecomplex-valued symbols, precoding of the complex-valued symbols, mappingof precoded complex-valued symbols to resource elements, generation ofcomplex-valued time-domain DFTS-OFDM/SC-FDMA signal for each antennaport, and/or the like.

Example modulation and up-conversion to the carrier frequency of thecomplex-valued DFTS-OFDM/SC-FDMA baseband signal for each antenna portand/or the complex-valued PRACH baseband signal is shown in FIG. 5B.Filtering may be employed prior to transmission.

An example structure for Downlink Transmissions is shown in FIG. 5C. Thebaseband signal representing a downlink physical channel may perform thefollowing processes. These functions are illustrated as examples and itis anticipated that other mechanisms may be implemented in variousembodiments. The functions include scrambling of coded bits in each ofthe codewords to be transmitted on a physical channel; modulation ofscrambled bits to generate complex-valued modulation symbols; mapping ofthe complex-valued modulation symbols onto one or several transmissionlayers; precoding of the complex-valued modulation symbols on each layerfor transmission on the antenna ports; mapping of complex-valuedmodulation symbols for each antenna port to resource elements;generation of complex-valued time-domain OFDM signal for each antennaport, and/or the like.

Example modulation and up-conversion to the carrier frequency of thecomplex-valued OFDM baseband signal for each antenna port is shown inFIG. 5D. Filtering may be employed prior to transmission.

FIG. 4 is an example block diagram of a base station 401 and a wirelessdevice 406, as per an aspect of an embodiment of the present disclosure.A communication network 400 may include at least one base station 401and at least one wireless device 406. The base station 401 may includeat least one communication interface 402, at least one processor 403,and at least one set of program code instructions 405 stored innon-transitory memory 404 and executable by the at least one processor403. The wireless device 406 may include at least one communicationinterface 407, at least one processor 408, and at least one set ofprogram code instructions 410 stored in non-transitory memory 409 andexecutable by the at least one processor 408. Communication interface402 in base station 401 may be configured to engage in communicationwith communication interface 407 in wireless device 406 via acommunication path that includes at least one wireless link 411.Wireless link 411 may be a bi-directional link. Communication interface407 in wireless device 406 may also be configured to engage in acommunication with communication interface 402 in base station 401. Basestation 401 and wireless device 406 may be configured to send andreceive data over wireless link 411 using multiple frequency carriers.According to aspects of an embodiments, transceiver(s) may be employed.A transceiver is a device that includes both a transmitter and receiver.Transceivers may be employed in devices such as wireless devices, basestations, relay nodes, and/or the like. Example embodiments for radiotechnology implemented in communication interface 402, 407 and wirelesslink 411 are illustrated are FIG. 1, FIG. 2, FIG. 3, FIG. 5, andassociated text.

An interface may be a hardware interface, a firmware interface, asoftware interface, and/or a combination thereof. The hardware interfacemay include connectors, wires, electronic devices such as drivers,amplifiers, and/or the like. A software interface may include codestored in a memory device to implement protocol(s), protocol layers,communication drivers, device drivers, combinations thereof, and/or thelike. A firmware interface may include a combination of embeddedhardware and code stored in and/or in communication with a memory deviceto implement connections, electronic device operations, protocol(s),protocol layers, communication drivers, device drivers, hardwareoperations, combinations thereof, and/or the like.

The term configured may relate to the capacity of a device whether thedevice is in an operational or non-operational state. Configured mayalso refer to specific settings in a device that effect the operationalcharacteristics of the device whether the device is in an operational ornon-operational state. In other words, the hardware, software, firmware,registers, memory values, and/or the like may be “configured” within adevice, whether the device is in an operational or nonoperational state,to provide the device with specific characteristics. Terms such as “acontrol message to cause in a device” may mean that a control messagehas parameters that may be used to configure specific characteristics inthe device, whether the device is in an operational or non-operationalstate.

According to various aspects of an embodiment, an LTE network mayinclude a multitude of base stations, providing a user planePDCP/RLC/MAC/PHY and control plane (RRC) protocol terminations towardsthe wireless device. The base station(s) may be interconnected withother base station(s) (for example, interconnected employing an X2interface). Base stations may also be connected employing, for example,an S1 interface to an EPC. For example, base stations may beinterconnected to the MME employing the S1-MME interface and to the S-G)employing the S1-U interface. The S1 interface may support amany-to-many relation between MMEs/Serving Gateways and base stations. Abase station may include many sectors for example: 1, 2, 3, 4, or 6sectors. A base station may include many cells, for example, rangingfrom 1 to 50 cells or more. A cell may be categorized, for example, as aprimary cell or secondary cell. At RRC connectionestablishment/re-establishment/handover, one serving cell may providethe NAS (non-access stratum) mobility information (e.g. TAI), and at RRCconnection re-establishment/handover, one serving cell may provide thesecurity input. This cell may be referred to as the Primary Cell(PCell). In the downlink, the carrier corresponding to the PCell may bethe Downlink Primary Component Carrier (DL PCC), while in the uplink,the carrier corresponding to the PCell may be the Uplink PrimaryComponent Carrier (UL PCC). Depending on wireless device capabilities,Secondary Cells (SCells) may be configured to form together with thePCell a set of serving cells. In the downlink, the carrier correspondingto an SCell may be a Downlink Secondary Component Carrier (DL SCC),while in the uplink, it may be an Uplink Secondary Component Carrier (ULSCC). An SCell may or may not have an uplink carrier.

A cell, comprising a downlink carrier and optionally an uplink carrier,may be assigned a physical cell ID and a cell index. A carrier (downlinkor uplink) may belong to only one cell. The cell ID or Cell index mayalso identify the downlink carrier or uplink carrier of the cell(depending on the context it is used). In the specification, cell ID maybe equally referred to a carrier ID, and cell index may be referred tocarrier index. In implementation, the physical cell ID or cell index maybe assigned to a cell. A cell ID may be determined using asynchronization signal transmitted on a downlink carrier. A cell indexmay be determined using RRC messages. For example, when thespecification refers to a first physical cell ID for a first downlinkcarrier, the specification may mean the first physical cell ID is for acell comprising the first downlink carrier. The same concept may apply,for example, to carrier activation. When the specification indicatesthat a first carrier is activated, the specification may also mean thatthe cell comprising the first carrier is activated.

Embodiments may be configured to operate as needed. The disclosedmechanism may be performed when certain criteria are met, for example,in a wireless device, a base station, a radio environment, a network, acombination of the above, and/or the like. Example criteria may bebased, at least in part, on for example, traffic load, initial systemset up, packet sizes, traffic characteristics, a combination of theabove, and/or the like. When the one or more criteria are met, variousexample embodiments may be applied. Therefore, it may be possible toimplement example embodiments that selectively implement disclosedprotocols.

A base station may communicate with a mix of wireless devices. Wirelessdevices may support multiple technologies, and/or multiple releases ofthe same technology. Wireless devices may have some specificcapability(ies) depending on its wireless device category and/orcapability(ies). A base station may comprise multiple sectors. When thisdisclosure refers to a base station communicating with a plurality ofwireless devices, this disclosure may refer to a subset of the totalwireless devices in a coverage area. This disclosure may refer to, forexample, a plurality of wireless devices of a given LTE release with agiven capability and in a given sector of the base station. Theplurality of wireless devices in this disclosure may refer to a selectedplurality of wireless devices, and/or a subset of total wireless devicesin a coverage area which perform according to disclosed methods, and/orthe like. There may be a plurality of wireless devices in a coveragearea that may not comply with the disclosed methods, for example,because those wireless devices perform based on older releases of LTEtechnology.

FIG. 6 and FIG. 7 are example diagrams for protocol structure with CAand DC as per an aspect of an embodiment of the present disclosure.E-UTRAN may support Dual Connectivity (DC) operation whereby a multipleRX/TX UE in RRC_CONNECTED may be configured to utilize radio resourcesprovided by two schedulers located in two eNB s connected via anon-ideal backhaul over the X2 interface. eNBs involved in DC for acertain UE may assume two different roles: an eNB may either act as anMeNB or as an SeNB. In DC a UE may be connected to one MeNB and oneSeNB. Mechanisms implemented in DC may be extended to cover more thantwo eNBs. FIG. 7 illustrates one example structure for the UE side MACentities when a Master Cell Group (MCG) and a Secondary Cell Group (SCG)are configured, and it may not restrict implementation. Media BroadcastMulticast Service (MBMS) reception is not shown in this figure forsimplicity.

In DC, the radio protocol architecture that a particular bearer uses maydepend on how the bearer is setup. Three alternatives may exist, an MCGbearer, an SCG bearer and a split bearer as shown in FIG. 6. RRC may belocated in MeNB and SRBs may be configured as a MCG bearer type and mayuse the radio resources of the MeNB. DC may also be described as havingat least one bearer configured to use radio resources provided by theSeNB. DC may or may not be configured/implemented in example embodimentsof the disclosure.

In the case of DC, the UE may be configured with two MAC entities: oneMAC entity for MeNB, and one MAC entity for SeNB. In DC, the configuredset of serving cells for a UE may comprise two subsets: the Master CellGroup (MCG) containing the serving cells of the MeNB, and the SecondaryCell Group (SCG) containing the serving cells of the SeNB. For a SCG,one or more of the following may be applied. At least one cell in theSCG may have a configured UL CC and one of them, named PSCell (or PCellof SCG, or sometimes called PCell), may be configured with PUCCHresources. When the SCG is configured, there may be at least one SCGbearer or one Split bearer. Upon detection of a physical layer problemor a random access problem on a PSCell, or the maximum number of RLCretransmissions has been reached associated with the SCG, or upondetection of an access problem on a PSCell during a SCG addition or aSCG change: a RRC connection re-establishment procedure may not betriggered, UL transmissions towards cells of the SCG may be stopped, anda MeNB may be informed by the UE of a SCG failure type. For splitbearer, the DL data transfer over the MeNB may be maintained. The RLC AMbearer may be configured for the split bearer. Like a PCell, a PSCellmay not be de-activated. A PSCell may be changed with a SCG change (forexample, with a security key change and a RACH procedure), and/orneither a direct bearer type change between a Split bearer and a SCGbearer nor simultaneous configuration of a SCG and a Split bearer may besupported.

With respect to the interaction between a MeNB and a SeNB, one or moreof the following principles may be applied. The MeNB may maintain theRRM measurement configuration of the UE and may, (for example, based onreceived measurement reports or traffic conditions or bearer types),decide to ask a SeNB to provide additional resources (serving cells) fora UE. Upon receiving a request from the MeNB, a SeNB may create acontainer that may result in the configuration of additional servingcells for the UE (or decide that it has no resource available to do so).For UE capability coordination, the MeNB may provide (part of) the ASconfiguration and the UE capabilities to the SeNB. The MeNB and the SeNBmay exchange information about a UE configuration by employing RRCcontainers (inter-node messages) carried in X2 messages. The SeNB mayinitiate a reconfiguration of its existing serving cells (for example, aPUCCH towards the SeNB). The SeNB may decide which cell is the PSCellwithin the SCG. The MeNB may not change the content of the RRCconfiguration provided by the SeNB. In the case of a SCG addition and aSCG SCell addition, the MeNB may provide the latest measurement resultsfor the SCG cell(s). Both a MeNB and a SeNB may know the SFN andsubframe offset of each other by OAM, (for example, for the purpose ofDRX alignment and identification of a measurement gap). In an example,when adding a new SCG SCell, dedicated RRC signaling may be used forsending required system information of the cell as for CA, except forthe SFN acquired from a MIB of the PSCell of a SCG.

In an example, serving cells may be grouped in a TA group (TAG). Servingcells in one TAG may use the same timing reference. For a given TAG,user equipment (UE) may use at least one downlink carrier as a timingreference. For a given TAG, a UE may synchronize uplink subframe andframe transmission timing of uplink carriers belonging to the same TAG.In an example, serving cells having an uplink to which the same TAapplies may correspond to serving cells hosted by the same receiver. AUE supporting multiple TAs may support two or more TA groups. One TAgroup may contain the PCell and may be called a primary TAG (pTAG). In amultiple TAG configuration, at least one TA group may not contain thePCell and may be called a secondary TAG (sTAG). In an example, carrierswithin the same TA group may use the same TA value and/or the sametiming reference. When DC is configured, cells belonging to a cell group(MCG or SCG) may be grouped into multiple TAGs including a pTAG and oneor more sTAGs.

FIG. 8 shows example TAG configurations as per an aspect of anembodiment of the present disclosure. In Example 1, pTAG comprises aPCell, and an sTAG comprises SCell1. In Example 2, a pTAG comprises aPCell and SCell, and an sTAG comprises SCell2 and SCell3. In Example 3,pTAG comprises PCell and SCell1, and an sTAG1 includes SCell2 andSCell3, and sTAG2 comprises SCell4. Up to four TAGs may be supported ina cell group (MCG or SCG) and other example TAG configurations may alsobe provided. In various examples in this disclosure, example mechanismsare described for a pTAG and an sTAG. Some of the example mechanisms maybe applied to configurations with multiple sTAGs.

In an example, an eNB may initiate an RA procedure via a PDCCH order foran activated SCell. This PDCCH order may be sent on a scheduling cell ofthis SCell. When cross carrier scheduling is configured for a cell, thescheduling cell may be different than the cell that is employed forpreamble transmission, and the PDCCH order may include an SCell index.At least a non-contention based RA procedure may be supported forSCell(s) assigned to sTAG(s).

FIG. 9 is an example message flow in a random access process in asecondary TAG as per an aspect of an embodiment of the presentdisclosure. An eNB transmits an activation command 600 to activate anSCell. A preamble 602 (Msg1) may be sent by a UE in response to a PDCCHorder 601 on an SCell belonging to an sTAG. In an example embodiment,preamble transmission for SCells may be controlled by the network usingPDCCH format 1A. Msg2 message 603 (RAR: random access response) inresponse to the preamble transmission on the SCell may be addressed toRA-RNTI in a PCell common search space (CSS). Uplink packets 604 may betransmitted on the SCell in which the preamble was transmitted.

According to an embodiment, initial timing alignment may be achievedthrough a random access procedure. This may involve a UE transmitting arandom access preamble and an eNB responding with an initial TA commandNTA (amount of timing advance) within a random access response window.The start of the random access preamble may be aligned with the start ofa corresponding uplink subframe at the UE assuming NTA=0. The eNB mayestimate the uplink timing from the random access preamble transmittedby the UE. The TA command may be derived by the eNB based on theestimation of the difference between the desired UL timing and theactual UL timing. The UE may determine the initial uplink transmissiontiming relative to the corresponding downlink of the sTAG on which thepreamble is transmitted.

The mapping of a serving cell to a TAG may be configured by a servingeNB with RRC signaling. The mechanism for TAG configuration andreconfiguration may be based on RRC signaling. According to variousaspects of an embodiment, when an eNB performs an SCell additionconfiguration, the related TAG configuration may be configured for theSCell. In an example embodiment, an eNB may modify the TAG configurationof an SCell by removing (releasing) the SCell and adding (configuring) anew SCell (with the same physical cell ID and frequency) with an updatedTAG ID. The new SCell with the updated TAG ID may initially be inactivesubsequent to being assigned the updated TAG ID. The eNB may activatethe updated new SCell and start scheduling packets on the activatedSCell. In an example implementation, it may not be possible to changethe TAG associated with an SCell, but rather, the SCell may need to beremoved and a new SCell may need to be added with another TAG. Forexample, if there is a need to move an SCell from an sTAG to a pTAG, atleast one RRC message, (for example, at least one RRC reconfigurationmessage), may be send to the UE to reconfigure TAG configurations byreleasing the SCell and then configuring the SCell as a part of thepTAG. When an SCell is added/configured without a TAG index, the SCellmay be explicitly assigned to the pTAG. The PCell may not change its TAgroup and may be a member of the pTAG.

The purpose of an RRC connection reconfiguration procedure may be tomodify an RRC connection, (for example, to establish, modify and/orrelease RBs, to perform handover, to setup, modify, and/or releasemeasurements, to add, modify, and/or release SCells). If the receivedRRC Connection Reconfiguration message includes the sCellToReleaseList,the UE may perform an SCell release. If the received RRC ConnectionReconfiguration message includes the sCellToAddModList, the UE mayperform SCell additions or modification.

In LTE Release-10 and Release-11 CA, a PUCCH may only be transmitted onthe PCell (PSCell) to an eNB. In LTE-Release 12 and earlier, a UE maytransmit PUCCH information on one cell (PCell or PSCell) to a given eNB.

As the number of CA capable UEs and also the number of aggregatedcarriers increase, the number of PUCCHs and also the PUCCH payload sizemay increase. Accommodating the PUCCH transmissions on the PCell maylead to a high PUCCH load on the PCell. A PUCCH on an SCell may beintroduced to offload the PUCCH resource from the PCell. More than onePUCCH may be configured for example, a PUCCH on a PCell and anotherPUCCH on an SCell. In the example embodiments, one, two or more cellsmay be configured with PUCCH resources for transmitting CSI/ACK/NACK toa base station. Cells may be grouped into multiple PUCCH groups, and oneor more cell within a group may be configured with a PUCCH. In anexample configuration, one SCell may belong to one PUCCH group. SCellswith a configured PUCCH transmitted to a base station may be called aPUCCH SCell, and a cell group with a common PUCCH resource transmittedto the same base station may be called a PUCCH group.

In an example embodiment, a MAC entity may have a configurable timertimeAlignmentTimer per TAG. The timeAlignmentTimer may be used tocontrol how long the MAC entity considers the Serving Cells belonging tothe associated TAG to be uplink time aligned. The MAC entity may, when aTiming Advance Command MAC control element is received, apply the TimingAdvance Command for the indicated TAG; start or restart thetimeAlignmentTimer associated with the indicated TAG. The MAC entitymay, when a Timing Advance Command is received in a Random AccessResponse message for a serving cell belonging to a TAG and/or if theRandom Access Preamble was not selected by the MAC entity, apply theTiming Advance Command for this TAG and start or restart thetimeAlignmentTimer associated with this TAG. Otherwise, if thetimeAlignmentTimer associated with this TAG is not running, the TimingAdvance Command for this TAG may be applied and the timeAlignmentTimerassociated with this TAG started. When the contention resolution isconsidered not successful, a timeAlignmentTimer associated with this TAGmay be stopped. Otherwise, the MAC entity may ignore the received TimingAdvance Command.

In example embodiments, a timer is running once it is started, until itis stopped or until it expires; otherwise it may not be running. A timercan be started if it is not running or restarted if it is running. Forexample, a timer may be started or restarted from its initial value.

Example embodiments of the disclosure may enable operation ofmulti-carrier communications. Other example embodiments may comprise anon-transitory tangible computer readable media comprising instructionsexecutable by one or more processors to cause operation of multi-carriercommunications. Yet other example embodiments may comprise an article ofmanufacture that comprises a non-transitory tangible computer readablemachine-accessible medium having instructions encoded thereon forenabling programmable hardware to cause a device (e.g. wirelesscommunicator, UE, base station, etc.) to enable operation ofmulti-carrier communications. The device may include processors, memory,interfaces, and/or the like. Other example embodiments may comprisecommunication networks comprising devices such as base stations,wireless devices (or user equipment: UE), servers, switches, antennas,and/or the like.

The amount of data traffic carried over cellular networks is expected toincrease for many years to come. The number of users/devices isincreasing and each user/device accesses an increasing number andvariety of services, e.g. video delivery, large files, images. This mayrequire not only high capacity in the network, but also provisioningvery high data rates to meet customers' expectations on interactivityand responsiveness. More spectrum may therefore needed for cellularoperators to meet the increasing demand. Considering user expectationsof high data rates along with seamless mobility, it may be beneficialthat more spectrum be made available for deploying macro cells as wellas small cells for cellular systems.

Striving to meet the market demands, there has been increasing interestfrom operators in deploying some complementary access utilizingunlicensed spectrum to meet the traffic growth. This is exemplified bythe large number of operator-deployed Wi-Fi networks and the 3GPPstandardization of LTE/WLAN interworking solutions. This interestindicates that unlicensed spectrum, when present, may be an effectivecomplement to licensed spectrum for cellular operators to helpaddressing the traffic explosion in some scenarios, such as hotspotareas. LAA may offer an alternative for operators to make use ofunlicensed spectrum while managing one radio network, thus offering newpossibilities for optimizing the network's efficiency.

In an example embodiment, Listen-before-talk (clear channel assessment)may be implemented for transmission in an LAA cell. In alisten-before-talk (LBT) procedure, equipment may apply a clear channelassessment (CCA) check before using the channel. For example, the CCAmay utilize at least energy detection to determine the presence orabsence of other signals on a channel in order to determine if a channelis occupied or clear, respectively. For example, European and Japaneseregulations mandate the usage of LBT in the unlicensed bands. Apart fromregulatory requirements, carrier sensing via LBT may be one way for fairsharing of the unlicensed spectrum.

In an example embodiment, discontinuous transmission on an unlicensedcarrier with limited maximum transmission duration may be enabled. Someof these functions may be supported by one or more signals to betransmitted from the beginning of a discontinuous LAA downlinktransmission. Channel reservation may be enabled by the transmission ofsignals, by an LAA node, after gaining channel access via a successfulLBT operation, so that other nodes that receive the transmitted signalwith energy above a certain threshold sense the channel to be occupied.Functions that may need to be supported by one or more signals for LAAoperation with discontinuous downlink transmission may include one ormore of the following: detection of the LAA downlink transmission(including cell identification) by UEs, time & frequency synchronizationof UEs, and/or the like.

In an example embodiment, a DL LAA design may employ subframe boundaryalignment according to LTE-A carrier aggregation timing relationshipsacross serving cells aggregated by CA. This may not imply that the eNBtransmissions can start only at the subframe boundary. LAA may supporttransmitting PDSCH when not all OFDM symbols are available fortransmission in a subframe according to LBT. Delivery of necessarycontrol information for the PDSCH may also be supported.

An LBT procedure may be employed for fair and friendly coexistence ofLAA with other operators and technologies operating in an unlicensedspectrum. LBT procedures on a node attempting to transmit on a carrierin an unlicensed spectrum may require the node to perform a clearchannel assessment to determine if the channel is free for use. An LBTprocedure may involve at least energy detection to determine if thechannel is being used. For example, regulatory requirements in someregions, for example, in Europe, may specify an energy detectionthreshold such that if a node receives energy greater than thisthreshold, the node assumes that the channel is not free. While nodesmay follow such regulatory requirements, a node may optionally use alower threshold for energy detection than that specified by regulatoryrequirements. In an example, LAA may employ a mechanism to adaptivelychange the energy detection threshold. For example, LAA may employ amechanism to adaptively lower the energy detection threshold from anupper bound. Adaptation mechanism(s) may not preclude static orsemi-static setting of the threshold. In an example a Category 4 LBTmechanism or other type of LBT mechanisms may be implemented.

Various example LBT mechanisms may be implemented. In an example, forsome signals, in some implementation scenarios, in some situations,and/or in some frequencies, no LBT procedure may performed by thetransmitting entity. In an example, Category 2 (for example, LBT withoutrandom back-off) may be implemented. The duration of time that thechannel is sensed to be idle before the transmitting entity transmitsmay be deterministic. In an example, Category 3 (for example, LBT withrandom back-off with a contention window of fixed size) may beimplemented. The LBT procedure may have the following procedure as oneof its components. The transmitting entity may draw a random number Nwithin a contention window. The size of the contention window may bespecified by the minimum and maximum value of N. The size of thecontention window may be fixed. The random number N may be employed inthe LBT procedure to determine the duration of time that the channel issensed to be idle before the transmitting entity transmits on thechannel. In an example, Category 4 (for example, LBT with randomback-off with a contention window of variable size) may be implemented.The transmitting entity may draw a random number N within a contentionwindow. The size of the contention window may be specified by a minimumand maximum value of N. The transmitting entity may vary the size of thecontention window when drawing the random number N. The random number Nmay be employed in the LBT procedure to determine the duration of timethat the channel is sensed to be idle before the transmitting entitytransmits on the channel.

LAA may employ uplink LBT at the UE. The UL LBT scheme may be differentfrom the DL LBT scheme (for example, by using different LBT mechanismsor parameters), since the LAA UL may be based on scheduled access whichaffects a UE's channel contention opportunities. Other considerationsmotivating a different UL LBT scheme include, but are not limited to,multiplexing of multiple UEs in a single subframe.

In an example, a DL transmission burst may be a continuous transmissionfrom a DL transmitting node with no transmission immediately before orafter from the same node on the same CC. A UL transmission burst from aUE perspective may be a continuous transmission from a UE with notransmission immediately before or after from the same UE on the sameCC. In an example, a UL transmission burst may be defined from a UEperspective. In an example, a UL transmission burst may be defined froman eNB perspective. In an example, in case of an eNB operating DL+UL LAAover the same unlicensed carrier, DL transmission burst(s) and ULtransmission burst(s) on LAA may be scheduled in a TDM manner over thesame unlicensed carrier. For example, an instant in time may be part ofa DL transmission burst or an UL transmission burst.

In an example embodiment, in an unlicensed cell, a downlink burst may bestarted in a subframe. When an eNB accesses the channel, the eNB maytransmit for a duration of one or more subframes. The duration maydepend on a maximum configured burst duration in an eNB, the dataavailable for transmission, and/or eNB scheduling algorithm. FIG. 10shows an example downlink burst in an unlicensed (e.g. licensed assistedaccess) cell. The maximum configured burst duration in the exampleembodiment may be configured in the eNB. An eNB may transmit the maximumconfigured burst duration to a UE employing an RRC configurationmessage.

The wireless device may receive from a base station at least one message(for example, an RRC) comprising configuration parameters of a pluralityof cells. The plurality of cells may comprise at least one license celland at least one unlicensed (for example, an LAA cell). Theconfiguration parameters of a cell may, for example, compriseconfiguration parameters for physical channels, (for example, a ePDCCH,PDSCH, PUSCH, PUCCH and/or the like).

Frame structure type 3 may be applicable to an unlicensed (for example,LAA) secondary cell operation. In an example, frame structure type 3 maybe implemented with normal cyclic prefix only. A radio frame may beT_(f)=307200. T_(s)=10 ms long and may comprise 20 slots of lengthT_(slot)=15360·T_(s)=0.5 ms, numbered from 0 to 19. A subframe may bedefined as two consecutive slots where subframe i comprises of slots 2iand 2i+1. In an example, the 10 subframes within a radio frame may beavailable for downlink and/or uplink transmissions. Downlinktransmissions may occupy one or more consecutive subframes, startinganywhere within a subframe and ending with the last subframe eitherfully occupied or following one of the DwPTS durations in a 3GPP Framestructure 2 (TDD frame). When an LAA cell is configured for uplinktransmissions, frame structure 3 may be used for both uplink or downlinktransmission.

An eNB may transmit one or more RRC messages to a wireless device (UE).The one or more RRC messages may comprise configuration parameters of aplurality of cells comprising one or more licensed cells and/or one ormore unlicensed (for example, Licensed Assisted Access-LAA) cells. Theone or more RRC messages may comprise configuration parameters for oneor more unlicensed (for example, LAA) cells. An LAA cell may beconfigured for downlink and/or uplink transmissions.

In an example, the configuration parameters may comprise a firstconfiguration field having a value of N for an LAA cell. The parameter Nmay be RRC configurable. N may be a cell specific or a UE specific RRCparameter. For example, N (for example, 6, 8, 16) may indicate a maximumnumber of HARQ processes that may be configured for UL transmissions. Inan example, one or more RRC messages may comprise configurationparameters of multi-subframe allocation parameters, maximum number ofHARQ processes in the uplink, and/or other parameters associated with anLAA cell.

In an example, a UE may receive a downlink control information (DCI)indicating uplink resources (resource blocks for uplink grant) foruplink transmissions.

In an example embodiment, persistent (also called burst ormulti-subframe) scheduling may be implemented. An eNB may scheduleuplink transmissions by self scheduling and/or cross scheduling. In anexample, an eNB may use UE C-RNTI for transmitting DCIs formulti-subframe grants. A UE may receive a multi-subframe DCI indicatinguplink resources (resource blocks for uplink grant) for more than oneconsecutive uplink subframes (a burst), for example m subframes. In anexample, a UE may transmit m subpackets (transport blocks-TBs), inresponse to the DCI grant. FIG. 11 shows an example multi-subframegrant, LBT process, and multi-subframe transmission.

In an example embodiment, an uplink DCI may comprise one or more fieldsincluding uplink RBs, a power control command, an MCS, the number ofconsecutive subframes (m), and/or other parameters for the uplink grant.

In an example, a multi-subframe DCI may comprise one or more parametersindicating that a DCI grant is a multi-subframe grant. A field in amulti-subframe DCI may indicate the number of scheduled consecutivesubframes (m). For example, a DCI for an uplink grant on an LAA cell maycomprise a 3-bit field. The value indicated by the 3-bit field mayindicate the number of subframes associated with the uplink DCI grant(other examples may comprise, for example, a 1-bit field or a 2-bitfield). For example, a value 000 may indicate a dynamic grant for onesubframe. For example, a field value 011 may indicate a DCI indicatinguplink resources for 4 scheduled subframes (m=field value in binary+1).In an example, RRC configuration parameters may comprise a firstconfiguration field having a value of N for an LAA cell. In an exampleimplementation, the field value may be configured to be less than N. Forexample, N may be configured as 2, and a maximum number of scheduledsubframes in a multi-subframe grant may be 2. In an example, N may beconfigured as 4 and a maximum number of scheduled subframes in amulti-subframe grant may be 4. In an example, N may be a number ofconfigured HARQ processes in an UL. Successive subframes on a carriermay be allocated to a UE when the UE receives a multi-subframe UL DCIgrant from an eNB.

At least one field included in a multi-subframe DCI may determinetransmission parameters and resource blocks used across m consecutivesubframes for transmission of one or more TBs. The DCI may comprise anassignment of a plurality of resource blocks for uplink transmissions.The UE may use the RBs indicated in the DCI across m subframes. The sameresource blocks may be allocated to the UE in m subframes as shown inFIG. 11.

A UE may perform listen before talk (LBT) before transmitting uplinksignals. The UE may perform an LBT procedure indicating that a channelis clear for a starting subframe of the one or more consecutive uplinksubframes. The UE may not perform a transmission at the startingsubframe if the LBT procedure indicates that the channel is not clearfor the starting subframe.

In an example embodiment, a wireless device may receive one or moreradio resource control (RRC) messages comprising configurationparameters for a licensed assisted access (LAA) cell. The one or moreRRC messages may comprise one or more consecutive uplink subframeallocation configuration parameters. In an example, the one or moreconsecutive uplink subframe allocation configuration parameterscomprises a first field, N.

A wireless device may receive a downlink control information (DCI)indicating uplink resources in a number of one or more consecutiveuplink subframes of the LAA cell. The DCI may comprise: the number ofthe one or more consecutive uplink subframes (m); an assignment of aplurality of resource blocks; and a transmit power control command. Thefirst field may indicate an upper limit for the number of the one ormore consecutive uplink subframes.

The wireless device may perform a listen before talk procedureindicating that a channel is clear for a starting subframe of the one ormore consecutive uplink subframes. The wireless device may transmit oneor more transport blocks, via the plurality of resource blocks usedacross the one or more consecutive uplink subframes. At least one fieldincluded in a multi-subframe DCI may determine transmission parametersand resource blocks used across m consecutive subframes for transmissionof one or more TBs. The DCI may comprise an assignment of a plurality ofresource blocks for uplink transmissions. The UE may use the RBsindicated in the DCI across m subframes. The same resource blocks may beallocated to the UE in m subframes.

A DCI indicating a multi-subframe grant (MSFG) may be supported incarrier aggregation, for example, for an unlicensed cell (e.g. an LAAcell). Design of a multi-subframe grant (MSFG) may take into account thedesign of existing DCIs used for single subframe grants. For example,current LTE-A DCI Format 0 and 4 may be used for uplink grants with andwithout special multiplexing. DCI Format 0 and 4 may be updated tosupport MSFGs with or without special multiplexing.

A MSFG may allow a UE to transmit on multiple consecutive uplinksubframes based on some common set of transmission parameters. Some oftransmission parameters, like MCS level, power control command, and/orresource assignments (e.g. RBs) may be common across scheduledsubframes. Some parameters, like HARQ process ID, RV and/or NDI may besubframe specific. The DCI indicating a MSFG may comprise one or moreparameters indicating the number of consecutive subframes allowed fortransmission according to the grant. In an example, the parameters whichmay be configured by DCI may include the number of consecutive subframes(m) associated with the MSFG. A MSFG may provide resource allocation forsubframes starting from subframe n and ending at subframe n+m−1.

When a UE receives a multi-subframe grant (MSFG) for UL transmissions ofm consecutive subframes on an LAA carrier, the UE may perform LBT beforetransmission on the scheduled subframes. A successful LBT may befollowed by a reservation signal if transmission of the reservationsignals is allowed and/or needed. The UE's LBT may or may not succeedbefore start of a first allowed transmission symbol of subframe n. In anexample, if UE's LBT is successful before a first allowed transmissionsymbol of subframe n, the UE may transmit data according tomulti-subframe DCI. The UE may transmit data (TBs) when LBT issuccessful.

The DCI indicating a MSFG may include parameters for UEs behavior due toLBT. A multi-subframe DCI may include possible LBT time interval(s)and/or at least one LBT configuration parameter. The DCI may indicateone or more configuration parameters for LBT process beforetransmissions corresponding to a MSFG.

In an example, one or more DCI may indicate configuration fortransmission of reservation signals, format of reservation signals,allowed starting symbol, and/or LBT intervals/symbols associated with aMSFG. For example, the DCI may indicate a PUSCH starting position in asubframe. LBT procedure may be performed before the PUSCH startingposition. One or more DCI may comprise configuration parametersindicating reservation signals and/or partial subframe configuration. Inan example embodiment, transmission of reservation signals and/orpartial subframe for a multi-subframe grant may not be supported.

In an example, a UE may perform LBT (e.g. in a symbol) before subframe nstarts. In an example, a UE may perform LBT in a first symbol ofsubframe n. A UE may be configured to perform LBT in one or more allowedsymbols of a subframe, or within a configured period/interval in asubframe. The multi-subframe grant DCI may include possible LBT timeinterval(s) and/or at least one LBT configuration parameter. Forexample, DCI may indicate that PUSCH starts in symbol 0 and a LBTprocedure is performed before PUSCH starts (e.g. last symbol of aprevious subframe). For example, DCI may indicate that PUSCH starts insymbol 1 and an LBT procedure is performed before PUSCH starts (e.g. insymbol 0).

In an example, one or more LBT configuration parameters may be indicatedin an RRC message. In an example, one or more RRC message configuring anLAA cell may comprise at least one field indicating an LBT interval.

An eNB may transmit to a UE one or more RRC messages comprisingconfiguration parameters of a plurality of cells. The plurality of cellsmay comprise one or more licensed cell and one or more unlicensed (e.g.LAA) cells. The eNB may transmit one or more DCIs for one or morelicensed cells and one or more DCIs for unlicensed (e.g. LAA) cells toschedule downlink and/or uplink TB transmissions on licensed/LAA cells.

A UE may receive at least one downlink control information (DCI) from aneNB indicating uplink resources in m subframes of a licensed assistedaccess (LAA) cell. In an example embodiment, an MSFG DCI may includeinformation about RV, NDI and HARQ process ID of a subframe of thegrant. For example, when a grant is for m subframes, the grant mayinclude at least m set of RVs and NDIs for HARQ processes associatedwith m subframes in the grant. In an example, subframe specificparameters may comprise one or more of the following for each subframeof a MSFG burst: M bits for RV, example 2 bits for 4 redundancyversions; and/or 1 bit for NDI.

In an example, common parameters may include: TPC for PUSCH, Cyclicshift for DM RS, resource block assignment, MCS and/or spatialmultiplexing parameters (if any, for example included in DCI format 4),LBT related parameters applied to the uplink burst, and/or Otherparameters, e.g. one or more multi-subframe configuration parameters.The MSFG DCI may comprise an RB assignment field, an MCS field, an TPCfield, an LBT field applicable to all the subframes associated with aMSFG. These parameters may be the same for different subframes of a MSFGburst. Resource block assignment, MCS and/or spatial multiplexingparameters may change from one MSFG burst to another MSFG burst.

An eNB may transmit to a UE a MSFG DCI including an SRS request for anLAA cell. There is a need to define mechanisms for an SRS transmissionin an LAA cell when a UE receives a MSFG DCI comprising an SRS request.There is a need to define an offset k, which may determine earliest timeSRS transmission may be made after the receipt of an SRS request. In anLAA cell, a UE's access to the channel for SRS transmission may besubject to some LBT requirements and/or COT limitation. There is a needto implement mechanisms to determine timing of aperiodic SRStransmission(s) within an uplink MSFG burst.

In an example embodiment, an eNB may transmit to a UE at least one RRCmessage comprising configuration parameters of one or more licensedcells and one or more unlicensed cells. The configuration parameters maycomprise SRS configuration parameters. One or more SRS configurationparameters may be common parameters and one or more SRS configurationparameters may be dedicated parameters. Example SRS RRC configurationparameters are presented in the specifications. In an exampleembodiment, a set of parameters, e.g. srs-ConfigApDCI-Format0 may beconfigured by RRC for aperiodic SRS, e.g. triggered using DCI Format 0.For example, a common set of parameters srs-ConfigApDCI-Format1a2b2c maybe configured by RRC, e.g. for aperiodic SRS using DCI formats 1A/2B/2C.In an example, three sets of SRS parameters, srs-ConfigApDCI-Format4,may be configured by RRC for aperiodic SRS using DCI Format 0 and/or 4.

Some of the configuration parameters of aperiodic SRS may be configuredby RRC. Aperiodic SRS may be triggered by an SRS request field in a UEspecific DCI. For example, PDCCH DCI Formats 0/4/1A (for FDD and TDD)and DCI Formats 2B/2C for TDD may include an SRS request field.

In an example embodiment, an uplink MSFG DCI may further comprise an SRSrequest field. The SRS request (e.g. 2 bits) may be used to triggeraperiodic sounding reference signal (SRS). In an example, the SRS may betriggered using one of up to three preconfigured settings. In anexample, for aperiodic SRS trigger, a 1-bit SRS request field may beused. In an example, a DCI may include a 2-bit SRS request field toindicate which of three configured parameters set to be used accordingto a pre-specified configuration table.

In an example embodiment, aperiodic SRS may be triggered by an SRSrequest field in a UE specific DCI. For example, an uplink MSFG DCI mayinclude an SRS request field. The RRC configuration parameters maycomprise configuration parameters of a DCI for SRS trigger. For example,configuration parameters may include an index of the DCI request fieldfor a UE in the DCI. RRC configuration parameters may comprise anaperiodic SRS time domain (subframe) RRC configuration parameteremployed for determining a subframe for aperiodic SRS transmission. Whena UE receives a MSFG DCI comprising an SRS request, the UE may transmitan SRS in an SRS subframe opportunity that occurs in the multi-subframeuplink burst. The SRS subframe opportunity may depend on a UE specificSRS RRC configuration parameter(s).

A wireless device may receive one or more radio resource control (RRC)messages comprising configuration parameters for a licensed assistedaccess (LAA) cell. The configuration parameters may comprise anaperiodic sounding reference signal (SRS) subframe parameter. In anexample, a wireless device may receive a MSFG DCI indicating uplinkresources in a number of one or more consecutive subframes of the LAAcell. The DCI may trigger an SRS transmission. The DCI may comprise afield indicating the number of one or more consecutive subframes, and/orone or more LBT configuration parameters (e.g. LBT type, LBT priorityclass, and/or LBT symbol). The wireless device may determine a positionof a first subframe in the one or more consecutive subframes based, atleast in part, on the aperiodic SRS subframe parameter. The wirelessdevice may transmit, in the first subframe, the SRS on the LAA cell. Thewireless device may transmit, in the first subframe, the SRS on the LAAcell when the wireless device is allowed to transmit in the firstsubframe according to an LBT procedure based on the LBT configurationparameter(s). The aperiodic SRS subframe parameter may indicate anoffset from the first (starting) scheduled subframe in a MSFG burst. Forexample, if the first scheduled subframe is subframe n, then the SRS istransmitted in subframe n+offset. In an example, an RRC configurationmay indicate that the starting subframe of a MSFG includes an aperiodicSRS when a MSFG DCI triggers SRS transmission. In an example, an RRCconfiguration may indicate that the second (next to the starting)subframe of a MSFG includes an aperiodic SRS when a MSFG DCI triggersSRS transmission. An example is shown in FIG. 13. Other examples may beprovided.

Example embodiments provide an efficient mechanism for determining whichsubframe of a MSFG includes an SRS signal when a MSFG DCI includes anSRS request field triggering aperiodic SRS. Configuring SRS subframe foran aperiodic SRS configuration (trigger type 1) for an LAA cell enablesan eNB to semi-statically communicate which subframe in a MSFG burstincludes an SRS. Example embodiments enable a UE to determine the SRSsubframe offset from the starting (first scheduled) MSFG subframe. Thestarting subframe is dynamically signaled using DCI signaling. In thismechanism, SRS subframe is dynamically configured using a DCI timing,MSFG burst starting time, and semi-static RRC configuration parameter.This mechanism may avoid including an SRS position field and/or triggerfield for each subframe associated with a MSFG and may reduce RRCsignaling and PDCCH overhead. Example embodiments may enhance downlinkspectral efficiency by reducing control signaling overhead and mayenhance uplink radio efficiency by determining which subframe in a MSFGburst includes SRS transmission. Instead of transmitting SRS in eachsubframe of a MSFG burst, SRS is transmitted in one of the MSFG burstsubframes.

In an example, a UE configured for Aperiodic SRS transmission upondetection of a positive SRS request in subframe #n may commence SRStransmission in the first subframe satisfying subframe #n+k, e.g. k≥4and based, at least, on the aperiodic SRS time domain (subframe) radioresource configuration (RRC). When a UE receives a MSFG DCI comprisingan SRS request, the UE may transmit an SRS in an SRS subframeopportunity that occurs in a subframe associated with a MSFG.

In an example, an eNB may transmit a DCI triggering an aperiodic SRSrequest for one or more LAA cells. A UE configured for aperiodic SRStransmission on frame structure type 3, upon detection of a positive SRSrequest in subframe n, may start SRS transmission in a first subframesatisfying subframe #n+k, k≥4 and based on SRS time domain (subframe)RRC configuration if that subframe is available for uplink SRStransmission. When a UE receives a MSFG DCI comprising an SRS request,the UE may transmit an SRS in an SRS subframe opportunity that occurs ina MSFG burst. Availability of a subframe/symbol for uplink SRStransmission may be determined based on LAA uplink cell access rules,e.g. LBT and/or maximum COT.

In an example embodiment, SRS transmission subframes may be configureddynamically via a MSFG DCI. In an example embodiment, the DCI mayindicate a specific subframe within a MSFG burst for transmission ofaperiodic SRS request. For example, when an SRS is triggered an SRS maybe transmitted subframe identified by a subframe offset relative to thestarting subframe (first scheduled subframe) in a MSFG burst. In anexample, the DCI may comprise a 3 bit field indicating the offset.

In an example embodiment, a wireless device may receive one or moreradio resource control (RRC) messages comprising configurationparameters for a licensed assisted access (LAA) cell. The configurationparameters comprising one or more sounding reference signal (SRS)parameters. The wireless device may receive a MSFG DCI indicating uplinkresources in a number of one or more consecutive subframes of the LAAcell. The DCI may trigger an aperiodic SRS transmission. The DCI maycomprise a first field indicating the number of one or more consecutivesubframes and/or a second field indicating a position of a firstsubframe in the one or more consecutive subframes for transmission of anSRS, and/or a third field indicating a listen-before-talk (LBT)configuration. The second field may indicate an offset from the first(starting) scheduled subframe in a MSFG burst. For example, if the firstscheduled subframe is subframe n, then the SRS is transmitted insubframe n+offset. The second field may indicate an offset from thefirst (starting) scheduled subframe of a MSFT burst (the one or moreconsecutive subframes). The wireless device may transmit, on the LAAcell and in the first subframe the SRS. The wireless device maytransmit, on the LAA cell and in the first subframe, the SRS when thewireless device is allowed to transmit in the first subframe accordingto an LBT procedure based on the LBT configuration. An example is shownin FIG. 12. The MSFG DCI may further comprise a transmit power control(TPC) command employed, at least in part, for calculating a transmitpower for the SRS.

Example embodiments provide an efficient mechanism for determining whichsubframe of a MSFG includes an SRS signal when a MSFG DCI triggersaperiodic SRS. The eNB does not need to transmit multiple SRS requestfields in a MSFG DCI, each for a different subframe of the MSFG burst.Example embodiments enable a UE to determine the SRS subframe offsetfrom the starting MSFG subframe. This mechanism may not requireincluding multiple SRS fields in a MSFG DCI, one for each subframeassociated with a MSFG. Example embodiments may reduce the size of theDCI and PDCCH signaling overhead. Example embodiment may enhancedownlink spectral efficiency by reducing control signaling overhead andmay enhance uplink radio efficiency by determining which subframesincludes SRS transmission. Example embodiments enable a UE to determinethe SRS subframe offset from the starting (first scheduled) MSFGsubframe. The MSFG starting subframe and SRS subframe offset isdynamically signaled using DCI signaling. In this mechanism, SRSsubframe is dynamically configured using DCI signaling and MSFG burststarting symbol.

In an example embodiment, a UE may not reattempt channel access to sendSRS if the first SRS opportunity is unavailable. The UE may cancel theSRS trigger request if LBT indicates that the channel is unavailable.The UE may receive a new SRS trigger from the eNB and start LBT processfor an SRS transmission.

Upon receiving an SRS trigger on a DCI, one or more targeted UEs maycheck for channel availability through configured LBT parameters for afirst applicable SRS transmission opportunity, e.g. 4 subframes afterreceiving the trigger. Those UE's which find the channel available mayproceed and send SRS. In an example, for UEs who find the channel busy,the UE may drop the configured SRS transmission until a new SRS triggeris sent by the eNB. In an example, SRS may be transmitted in an uplinkMSFG burst and LBT may be performed for the uplink MSFG burst and no LBTmay be required just for the SRS transmission.

In an embodiment, a single SRS may be triggered by an eNB for a partialuplink subframe following an end partial downlink subframe. Suchsubframes may provide opportunities for an eNB to obtain SRS feedbackfrom one or multiple UEs who may be scheduled in uplink of the LAA cell.A UE may transmit SRS in a partial subframe even if the partial subframedo not coincide with SRS subframes if configured. Such transmissiontiming, which may be allowed through DCI based SRS triggers, may be inaddition to those configured by RRC.

In an example embodiment, an eNB may transmit a DCI comprising an SRSrequest field to trigger one or more UE's SRS transmission after end ofdownlink end partial subframe. In one example embodiment, UE'stransmitting on such partial uplink subframe may transmit SRS on thesame symbol like a full subframe. In an example, given uplink subframemay have multiple M available symbols, UEs may transmit SRS on multiplesymbols. This mechanism may be implemented when a UE transmits SRS onlast M symbols of a partial uplink subframe e.g. with some frequencyhopping between SRS transmissions. UEs may be grouped into M groupswhere a group transmits SRS on one of the last M symbols of uplinkpartial subframe.

In an example, if there are multiple SRS opportunities within durationof scheduled multi-subframe UL grant, the SRS may be transmitted onceand in an earliest SRS opportunity within a duration of schedulesubframes. This mechanism may allow the eNB to receive an SRS in anearliest opportunity. The eNB may process the SRS to obtain informationon channel estimation and/or uplink transmission timing. The eNB may usethe information for scheduling resources for downlink/uplinktransmissions corresponding to a UE.

In an example, if there are multiple SRS opportunities within durationof a scheduled multi-subframe UL grant, the SRS may be transmitted onceand in the latest SRS opportunity within duration of schedule subframes.This mechanism may allow the eNB to receive the SRS later (compared tothe first SRS opportunity). This mechanism may provide an eNB with themost up to date information on uplink channel condition and/or uplinktiming. The eNB may employ this information for subsequent uplink and/ordownlink grants.

According to various embodiments, a device such as, for example, awireless device, a base station and/or the like, may comprise one ormore processors and memory. The memory may store instructions that, whenexecuted by the one or more processors, cause the device to perform aseries of actions. Embodiments of example actions are illustrated in theaccompanying figures and specification.

FIG. 14 is an example flow diagram as per an aspect of an embodiment ofthe present disclosure. At 1410, a wireless device may receive one ormore radio resource control (RRC) messages comprising configurationparameters for a licensed assisted access (LAA) cell. The configurationparameters may comprise one or more sounding reference signal (SRS)parameters. At 1420, the wireless device may receive a downlink controlinformation (DCI) indicating uplink resources in a number of one or moreconsecutive subframes of the LAA cell. The DCI may comprise: a firstfield indicating the number of the one or more consecutive subframes; asecond field indicating a position of a first subframe in the one ormore consecutive subframes for transmission of an SRS; and a third fieldindicating a listen-before-talk (LBT) configuration. At 1430, thewireless device may transmit, on the LAA cell and in the first subframe,the SRS when the wireless device is allowed to transmit in the firstsubframe according to an LBT procedure based on the LBT configuration.

The SRS may be transmitted, for example, in more than one symbol of thefirst subframe. The one or more SRS parameters may comprise, forexample, an aperiodic SRS configuration parameter. The SRS may betransmitted, for example, in a last symbol of the first subframe. Thesecond field may indicate, for example, an offset from a startingsubframe of the one or more consecutive subframes. The DCI may indicate,for example, whether an SRS transmission in the one or more consecutivesubframes is triggered. The one or more SRS parameters may comprise, forexample, one or more common SRS parameters and one or more dedicated SRSparameters. According to an embodiment, the wireless device may furthertransmit one or more transport blocks in the first subframe. The SRS maybe transmitted, for example, in a last symbol of the first subframe. TheDCI may further comprise, for example, a transmit power control (TPC)command employed, at least in part, for calculating a transmit power forthe SRS.

FIG. 15 is an example flow diagram as per an aspect of an embodiment ofthe present disclosure. At 1510, a base station may transmit a downlinkcontrol information (DCI) indicating uplink resources in a number of oneor more consecutive subframes of a licensed assisted access (LAA) cell.The DCI may comprise: a first field indicating the number of the one ormore consecutive subframes; and a second field indicating a position ofa first subframe in the one or more consecutive subframes fortransmission of an SRS. At 1520, the base station may receive in thefirst subframe, the SRS on the LAA cell. The SRS may be received, forexample, in a last symbol of the first subframe.

FIG. 16 is an example flow diagram as per an aspect of an embodiment ofthe present disclosure. At 1610, a wireless device may receive adownlink control information (DCI) indicating uplink resources in one ormore subframes. The DCI may comprise a field indicating a position of asubframe in the one or more subframes for transmission of a soundingreference signal (SRS). At 1620, the wireless device may transmit theSRS in the subframe. The DCI may, for example, trigger a soundingreference signal (SRS) transmission. The DCI may comprise, for example,a second field indicating a number of the one or more subframes.

FIG. 17 is an example flow diagram as per an aspect of an embodiment ofthe present disclosure. At 1710, a base station may transmit a downlinkcontrol information (DCI) indicating uplink resources in one or moresubframes. The DCI may comprise a field indicating a position of asubframe in the one or more subframes for transmission of a soundingreference signal (SRS). At 1720, the base station may receive the SRS inthe subframe. The DCI may, for example, trigger a sounding referencesignal (SRS) transmission. The DCI may comprise, for example, a secondfield indicating a number of one or more subframes.

FIG. 18 is an example flow diagram as per an aspect of an embodiment ofthe present disclosure. At 1810, a wireless device may receive one ormore radio resource control (RRC) messages comprising configurationparameters for a licensed assisted access (LAA) cell. The configurationparameters may comprise an aperiodic sounding reference signal (SRS)subframe parameter. At 1820, the wireless device may receive a downlinkcontrol information (DCI) indicating uplink resources in a number of oneor more consecutive subframes of the LAA cell. The DCI may trigger anSRS transmission and may comprise: the number of the one or moreconsecutive subframes; and a listen-before-talk (LBT) configuration. At1830, the wireless device may determine a position of a first subframein the one or more consecutive subframes based, at least in part, on theaperiodic SRS subframe parameter. At 1840, the wireless device maytransmit, in the first subframe, the SRS on the LAA cell when thewireless device is allowed to transmit in the first subframe accordingto an LBT procedure based on the LBT configuration.

The SRS may be transmitted, for example, in more than one symbol of thefirst subframe. The DCI may further comprise, for example, a fieldindicating whether the SRS transmission is triggered. The SRS may betransmitted, for example, in a last symbol of the first subframe. Theaperiodic SRS subframe parameter may indicate, for example, an offsetfrom a starting subframe of the one or more consecutive subframes. TheLBT configuration may indicate, for example, that a symbol time intervalis employed for the LBT procedure. The configuration parameters maycomprise, for example, one or more common SRS parameters and one or morededicated SRS parameters. The wireless device may further transmit, forexample, one or more transport blocks in the first subframe. Theconfiguration parameters may comprise, for example, an SRS bandwidth.The DCI may further comprise, for example, a transmit power control(TPC) command employed, at least in part, for calculating a transmitpower for the SRS.

FIG. 19 is an example flow diagram as per an aspect of an embodiment ofthe present disclosure. At 1910, a base station may transmit one or moreradio resource control (RRC) messages comprising configurationparameters for a licensed assisted access (LAA) cell. The configurationparameters may comprise an aperiodic sounding reference signal (SRS)subframe parameter. At 1920, the base station may transmit a downlinkcontrol information (DCI) indicating uplink resources in a number of oneor more consecutive subframes of the LAA cell. The DCI may trigger anSRS transmission and may comprise a field indicating the number of theone or more consecutive subframes. At 1930, the base station mayreceive, in the first subframe, the SRS on the LAA cell wherein aposition of a first subframe in the one or more consecutive subframesdepends, at least, on a value of the aperiodic SRS subframe parameter.The DCI may further comprise, for example, a transmit power control(TPC) command employed, at least in part, for calculating a transmitpower for the SRS.

FIG. 20 is an example flow diagram as per an aspect of an embodiment ofthe present disclosure. At 2010, a wireless device may receive one ormore RRC messages comprising an aperiodic SRS subframe parameter. At2020, the wireless device may receive a DCI triggering an SRStransmission and indicating uplink resources in one or more subframes.At 2030, the wireless device may determine a position of a subframe inthe one or more subframes based, at least in part, on the aperiodic SRSsubframe parameter. At 2040, the wireless device may transmit the SRS inthe subframe. The RRC message may comprise, for example, configurationparameters for a LAA cell. The DCI may comprise, for example, a fieldindicating the number of the one or more subframes.

FIG. 21 is an example flow diagram as per an aspect of an embodiment ofthe present disclosure. At 2110, a base station may transmit one or moreRRC messages comprising an aperiodic SRS subframe parameter. At 2120,the base station may transmit a DCI triggering an SRS transmission andindicating uplink resources in one or more subframes. At 2130, the basestation may determine a position of a subframe in the one or moresubframes based, at least in part, on the aperiodic SRS subframeparameter. At 2140, the base station may receive the SRS in thesubframe. The RRC message may comprise, for example, configurationparameters for a LAA cell. The DCI may comprise, for example, a fieldindicating the number of the one or more subframes.

FIG. 22 is an example flow diagram as per an aspect of an embodiment ofthe present disclosure. At 2210, a wireless device may receive one ormore RRC messages comprising an aperiodic SRS subframe parameter. At2220, the wireless device may receive a DCI triggering an SRStransmission and indicating uplink resources in one or more subframes.At 2230, the wireless device may transmit the SRS in the subframe,wherein a position of the subframe in the one or more subframes isbased, at least in part, on the aperiodic SRS subframe parameter.

FIG. 23 is an example flow diagram as per an aspect of an embodiment ofthe present disclosure. At 2310, a base station may transmit one or moreRRC messages comprising an aperiodic SRS subframe parameter. At 2320,the base station may transmit a DCI triggering an SRS transmission andindicating uplink resources in one or more subframes. At 2330, the basestation may receive the SRS in the subframe. A position of the subframein the one or more subframes is determined based, at least in part, onthe aperiodic SRS subframe parameter.

In this specification, “a” and “an” and similar phrases are to beinterpreted as “at least one” and “one or more.” In this specification,the term “may” is to be interpreted as “may, for example.” In otherwords, the term “may” is indicative that the phrase following the term“may” is an example of one of a multitude of suitable possibilities thatmay, or may not, be employed to one or more of the various embodiments.If A and B are sets and every element of A is also an element of B, A iscalled a subset of B. In this specification, only non-empty sets andsubsets are considered. For example, possible subsets of B={cell1,cell2} are: {cell1}, {cell2}, and {cell1, cell2}.

In this specification, parameters (Information elements: IEs) maycomprise one or more objects, and each of those objects may comprise oneor more other objects. For example, if parameter (IE) N comprisesparameter (IE) M, and parameter (IE) M comprises parameter (IE) K, andparameter (IE) K comprises parameter (information element) J, then, forexample, N comprises K, and N comprises J. In an example embodiment,when one or more messages comprise a plurality of parameters, it impliesthat a parameter in the plurality of parameters is in at least one ofthe one or more messages, but does not have to be in each of the one ormore messages.

Many of the elements described in the disclosed embodiments may beimplemented as modules. A module is defined here as an isolatableelement that performs a defined function and has a defined interface toother elements. The modules described in this disclosure may beimplemented in hardware, software in combination with hardware,firmware, wetware (i.e hardware with a biological element) or acombination thereof, all of which are behaviorally equivalent. Forexample, modules may be implemented as a software routine written in acomputer language configured to be executed by a hardware machine (suchas C, C++, Fortran, Java, Basic, Matlab or the like) or amodeling/simulation program such as Simulink, Stateflow, GNU Octave, orLabVIEWMathScript. Additionally, it may be possible to implement modulesusing physical hardware that incorporates discrete or programmableanalog, digital and/or quantum hardware. Examples of programmablehardware comprise: computers, microcontrollers, microprocessors,application-specific integrated circuits (ASICs); field programmablegate arrays (FPGAs); and complex programmable logic devices (CPLDs).Computers, microcontrollers and microprocessors are programmed usinglanguages such as assembly, C, C++ or the like. FPGAs, ASICs and CPLDsare often programmed using hardware description languages (HDL) such asVHSIC hardware description language (VHDL) or Verilog that configureconnections between internal hardware modules with lesser functionalityon a programmable device. Finally, it needs to be emphasized that theabove mentioned technologies are often used in combination to achievethe result of a functional module.

The disclosure of this patent document incorporates material which issubject to copyright protection. The copyright owner has no objection tothe facsimile reproduction by anyone of the patent document or thepatent disclosure, as it appears in the Patent and Trademark Officepatent file or records, for the limited purposes required by law, butotherwise reserves all copyright rights whatsoever.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example, and notlimitation. It will be apparent to persons skilled in the relevantart(s) that various changes in form and detail can be made thereinwithout departing from the spirit and scope. In fact, after reading theabove description, it will be apparent to one skilled in the relevantart(s) how to implement alternative embodiments. Thus, the presentembodiments should not be limited by any of the above describedexemplary embodiments. In particular, it should be noted that, forexample purposes, the above explanation has focused on the example(s)using FDD communication systems. However, one skilled in the art willrecognize that embodiments of the disclosure may also be implemented ina system comprising one or more TDD cells (e.g. frame structure 2 and/orframe structure 3-licensed assisted access). The disclosed methods andsystems may be implemented in wireless or wireline systems. The featuresof various embodiments presented in this disclosure may be combined. Oneor many features (method or system) of one embodiment may be implementedin other embodiments. Only a limited number of example combinations areshown to indicate to one skilled in the art the possibility of featuresthat may be combined in various embodiments to create enhancedtransmission and reception systems and methods.

In addition, it should be understood that any figures which highlightthe functionality and advantages, are presented for example purposesonly. The disclosed architecture is sufficiently flexible andconfigurable, such that it may be utilized in ways other than thatshown. For example, the actions listed in any flowchart may bere-ordered or only optionally used in some embodiments.

Further, the purpose of the Abstract of the Disclosure is to enable theU.S. Patent and Trademark Office and the public generally, andespecially the scientists, engineers and practitioners in the art whoare not familiar with patent or legal terms or phraseology, to determinequickly from a cursory inspection the nature and essence of thetechnical disclosure of the application. The Abstract of the Disclosureis not intended to be limiting as to the scope in any way.

Finally, it is the applicant's intent that only claims that include theexpress language “means for” or “step for” be interpreted under 35U.S.C. 112. Claims that do not expressly include the phrase “means for”or “step for” are not to be interpreted under 35 U.S.C. 112.

What is claimed is:
 1. A method comprising: receiving, by a wirelessdevice, a radio resource control message comprising an aperiodicsounding reference signal (SRS) subframe parameter; receiving a downlinkcontrol information: indicating uplink resources in a plurality ofscheduled consecutive subframes for transmission of transport blocks bythe wireless device; and triggering an SRS transmission in a subframe ofthe plurality of scheduled consecutive subframes; and transmitting theSRS in the subframe, wherein a position of the subframe in the pluralityof scheduled consecutive subframes is determined based on the aperiodicSRS subframe parameter.
 2. The method of claim 1, wherein the downlinkcontrol information comprises a first field indicating a number of theplurality of scheduled consecutive subframes.
 3. The method of claim 1,wherein the SRS is transmitted in more than one symbol of the subframe.4. The method of claim 1, wherein the aperiodic SRS subframe parameterindicates an offset from a starting subframe of the plurality ofscheduled consecutive subframes.
 5. The method of claim 1, wherein thedownlink control information comprises a listen-before-talk (LBT)configuration for an LBT procedure.
 6. The method of claim 5, whereinthe SRS is based on the LBT procedure indicating a clear channel.
 7. Themethod of claim 5, wherein the LBT configuration indicates a symbol timeinterval is employed for the LBT procedure.
 8. The method of claim 1,wherein the downlink control information further comprises a fieldindicating whether transmission of the SRS is triggered.
 9. The methodof claim 1, wherein the SRS is transmitted in a last symbol of thesubframe.
 10. The method of claim 1, wherein the radio resource controlmessage further comprise one or more common SRS parameters and one ormore dedicated SRS parameters.
 11. A wireless device comprising: one ormore processors; and memory storing instructions that, when executed bythe one or more processors, cause the wireless device to: receive aradio resource control message comprising an aperiodic soundingreference signal (SRS) subframe parameter; receive a downlink controlinformation: indicating uplink resources in a plurality of scheduledconsecutive subframes for transmission of transport blocks by thewireless device; and triggering an SRS transmission in a subframe of theplurality of scheduled consecutive subframes; and transmit the SRS inthe subframe, wherein a position of the subframe in the plurality ofscheduled consecutive subframes is determined based on the aperiodic SRSsubframe parameter.
 12. The wireless device of claim 11, wherein thedownlink control information comprises a first field indicating a numberof the plurality of scheduled consecutive subframes.
 13. The wirelessdevice of claim 11, wherein the SRS is transmitted in more than onesymbol of the subframe.
 14. The wireless device of claim 11, wherein theaperiodic SRS subframe parameter indicates an offset from a startingsubframe of the plurality of scheduled consecutive subframes.
 15. Thewireless device of claim 11, wherein the downlink control informationcomprises a listen-before-talk (LBT) configuration for an LBT procedure.16. The wireless device of claim 15, wherein the SRS is based on the LBTprocedure indicating a clear channel.
 17. The wireless device of claim15, wherein the LBT configuration indicates a symbol time interval isemployed for the LBT procedure.
 18. The wireless device of claim 11,wherein the downlink control information further comprises a fieldindicating whether transmission of the SRS is triggered.
 19. Thewireless device of claim 11, wherein the SRS is transmitted in a lastsymbol of the subframe.
 20. A system comprising: a base stationcomprising: one or more first processors; and first memory storing firstinstructions that, when executed by the one or more first processors,cause the base station to: transmit a radio resource control messagecomprising an aperiodic sounding reference signal (SRS) subframeparameter; transmit a downlink control information; and a wirelessdevice comprising: one or more second processors; and second memorystoring second instructions that, when executed by the one or moresecond processors, cause the wireless device to: receive the radioresource control message; receive the downlink control information,wherein the downlink control information: indicates uplink resources ina plurality of scheduled consecutive subframes for transmission oftransport blocks by the wireless device; and triggers an SRStransmission in a subframe of the plurality of scheduled consecutivesubframes; and transmit the SRS in the subframe, wherein a position ofthe subframe in the plurality of scheduled consecutive subframes isdetermined based on the aperiodic SRS subframe parameter.